(1) Field of the Invention
The present invention relates to an improved cooling system for an airfoil portion of a turbine engine component and to a method of making same.
(2) Prior Art
Existing designs of turbine engine components, such as turbine blades, formed using refractory metal core (RMC) elements have peripheral cooling circuits placed around the airfoil portion of the turbine engine components to cool the airfoil portion metal convectively. FIG. 1 illustrates a pressure side view of one such turbine engine component, while FIG. 2 illustrates a suction side view of the turbine engine component. In some instances, the axial internal cores end in film cooling slots. The combination of film and convective cooling of peripheral microcircuits lead to significant increases in the overall cooling effectiveness. This in turn leads to extended life capability for the airfoil portion using the same amount of cooling flow as existing cooling design or less.
Existing airfoil configurations are highly three dimensional as illustrated in FIGS. 1 and 2, forming RMC elements to conform to the different airfoil shapes can be difficult, as residual stress tend to spring these core elements back to the undeformed shaped during casting. As a result, positional tolerances may be difficult to maintain during the casting preparation phases, when the wax and the core elements are assembled together. During investment casting, as the liquid metal is introduced in the casting pattern, the temperature that the cores are subject to can lead to deformation of the RMC elements, particularly if residual stress exists due to pre-form conditions.
It is desirable to minimize the consequences of pre-form operations.